Which leaves us with a sticky dilemma. Do we broach the subject with my sister? Or do we address it with the boyfriend? Or perhaps it's better if we don't say anything at all? On the one hand, I don't want my sister dating somebody who's just not that into her. On the other hand, I don't want to create an emerging-sexuality-embarrassment for the boyfriend. What do we do?

— Sister's Keeper

Dear Keeper,

This is quite the — how shall I put this? — multi-pronged dilemma, so I took it to a few expert chums to get their take. Don't worry, I didn't name anybody.

First up, I need to stress that what we have here is not a "sexual preference" issue. The gay bit is peripheral. It's 2016. Dudes who are going around sexting other dudes are not going to experience "emerging-sexuality-embarrassment".

So what we have here is cheating issue, or at least a potential cheating issue, and we shall treat it as such.

The advice I heard was split almost exclusively along gender lines, just like a 1987 wedding where all the men get the beef and the women get the salmon. Males tended to view your sister as a damsel in distress, and declared that you should confront her beef-and-salmon-hogging cad at once, send him on his way, with the help of a few elaborate gladiatorial weapons if needs be, and preserve your sister's fair heart.

"At least 87 percent of women agree that 'because he's gay' is the number one preferred reason for being dumped"

Women, however, almost universally felt that your sister had been deceived quite enough, thanks, and any further cover-ups would only make her feel more embarrassed if she got wind of them. Tell her straight-up, came the call from the ladies, or get your mum to do it as she's probably less likely to charge in there with a megaphone and a cattleprod, and let your sister decide how she wants to handle it from there.

A third much smaller group made mewling sounds to the effect of letting things sort themselves out naturally — using the premise that your sister might be unable to cope with the heartbreak of losing her paramour — but I swiftly shot that nonsense down. At least 87 percent of women agree that "because he's gay" is the number one preferred reason for being dumped, certainly ahead of falling for some other girl or, the most awful sentence in the English language, "I just really need to concentrate on my work right now".

Then there was a final group — gay males — who, after demanding to see these provocative photos for themselves before they could make a considered judgement, turned the spotlight not on your sister's boyfriend, Keeper, but on your brother.

"A 17-year-old kid wouldn't send photos like that unless he had good reason to," said one. "Are you sure the brother didn't give him reason to believe the approach was wanted?" said another. Has there ever been a gay male who didn't think the solution to all problems was more coming out parties?

These groups are all so well-meaning, Keeper, and yet all so wrong. The gossip mill has already worked overtime on this most gossip-worthy matter, but now it needs to rest. Involve no other person, instruct your younger brother to speak to the boyfriend and lay down a friendly, jousting stick-free ultimatum: "Tell my sister you're gay, or I'm telling her about the photos."

The only reason we're in this mess is because everyone involved has avoided telling everyone else how they really feel, so now it's time to come clean.

And if your brother doesn't do his duty, Keeper, you can pass on this message from me: I'll do it for him.

Alexandra Carltonis a Sydney-based journalist, wife and mum of a nine-year-old boy. Fifteen years of interviewing psychologists, scientists, politicians, taste-makers and other highly-qualified people means she's very good at stealing their smart thoughts and passing them off as her own in order to amaze and delight at social gatherings. She's obsessed with documentaries, cool sneakers, ranking her favourite American presidents and starting new, very brief, health regimes. Oh, and she loves solving people's problems. Except her own.